This invention relates to distributed processing systems, and in particular, to systems and methods for performing text or word processing in a distributed processing environment.
Early text processing on computers involved a mainframe coupled to a teletype printer terminal. The teletype hardware only allowed information to be transferred from the teletype to the main frame whenever each key was depressed. Text editing was limited to at most a single line by the physical characteristics of such a device.
When cathode ray tube (CRT) technology developed for use with computers, CRT text processors continued to offer only single line editing since they were adapted from the teletype text processors. Later screen editors which utilized block mode terminals allowed processing of changes for an entire screen of text.
A typical full-screen text processor for a CRT terminal coupled to a mainframe processor is very slow because the terminal sends each key stroke to the main frame for processing. Since mainframes support many other tasks, the response time for text processing is usually unacceptably slow.
Dedicated text processing emerged with the advent of minicomputers and personal computers. Dedicated text processors, as their name indicates, provide only text editing and usually only for a single user. These systems provide relatively fast response times, but they have several disadvantages which make them unacceptable for many business applications. Small, dedicated processors typically have very limited storage which limits the size of the files or documents that dedicated processors can accept. Data sharing is also a problem because any such data must be stored on a transportable medium, for example a floppy disc, and it must be stored in a format which is recognizable to the recipient computer. This is a very slow and awkward method of data sharing.
A more significant drawback to most dedicated text processing implemented on a personal computer is that floppy disc storage is prone to error and degradation which cause loss of files and data with potentially disastrous results.
A new trend in the data processing field involves distributed processing, an example of which is shown in FIG. 1. In a distributed data processing system, a host processor 10 communicates with remote terminals 20 via communication lines 30. The terminals in a distributed data processing system have enough processing capability to perform certain operations, the amount of processing capability varying with the system.
A problem encountered in designing distributed processing systems is dividing the labor between the host computer and the distributed terminals to take advantage of the terminals' speed and the host's memory and processing capability.
Accordingly, an object of this invention is to provide text processing in a distributed processing environment which offers fast response time.
Another object of this invention is to provide text processing in a distributed processing environment which maintains high data integrity.
Yet another object of the invention is to provide text processing in a distributed processing environment that uses the host's computer memory capability and processing speed but does not sacrifice response time by subjecting the remote terminals to the unpredictable availability of the host's resources in a time-sharing environment.
A further object of the invention is to provide a distributed processing system and method of operating such a system which efficiently manages communications between the host computer and remote terminals.